Catalyst-free synthesis and luminescence of aligned ZnO nanorods

Quasi-aligned undoped ZnO nanorods with diameter in the range 100-300 nm and length of several micrometers have been grown catalyst-free on Si(1 0 0) wafer in a one-step process by direct heating of Zn powders. All nanowires are single crystals and are aligned vertically to the substrate surface with c-axis preferred orientation. XRD, HRTEM and Raman studies revealed that the ZnO nanorods have wurtzite phase, are highly crystalline and well aligned with the lattice parameters a=0.32 nm and c=0.52 nm. The PL spectra measured at different temperatures are dominated by excitonic emission at ∼380 nm and less intense below band gap emission band centered at 520 nm.